Method and apparatus for loading programs in a distributed processing system

ABSTRACT

A system for loading a program in a distributed processing system including a plurality of information processing units interconnected by a transmission system. An information processing unit prepares a program and sends the program to the transmission system. Another information processing unit receives the program from the transmission system and stores the program in a memory in accordance with a content code of the program. A program based on program may be retrieved from the memory structural information, and sent to the transmission system. Each information processing unit includes a device for sending program structural information to the transmission system, selecting a corresponding program from the transmission system and loading the selected program in the unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a distributed processing system comprising a plurality of information processing units interconnected by a data transmission system, and more particularly to a method for program loading by coordination of the distributed information processing units. p 2. Description of the Prior Art

In a prior art distributed system, when a program is to be loaded to a plurality of subsystems, a subsystem which developed the program functions as a master station, grasps a memory map of the subsystems to which the program is to be loaded and directly loads the program to them. Accordingly, if a system configuration changes due to memory allocation of the loading subsystem, or expansion or maintenance of the subsystems, it becomes impossible to load the program.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for program loading which permits loading of a latest program to a started subsystem, without requiring a central management device for program loading. The method and apparatus of the present invention operates in a distributed system in which a system configuration always changes with maintenance, failure or expansion and a program per se also gradually changes by function enhancement.

In order to achieve the above object, the present invention provides a distributed processing system comprising a plurality of information processing units interconnected by a data transmission system, is provided wherein a program is prepared in one of the information processing units and sent to the data transmission system; the program is received in one of the other information processing units, a content code thereof is checked, and the program is stored in a memory; based on program structural information the corresponding program is retrieved and sent to the transmission system; program structural information of the other information processing units is sent to the transmission system; and a corresponding program is selected from the transmission system and loaded to the information processing unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall configuration of a system;

FIG. 2 shows a configuration of an information processing unit which serves as a subsystem;

FIG. 3 shows a format of a message which flows on a transmission system;

FIG. 4 shows transmission and reception status of the message;

FIG. 5 shows a format of a message which uses a program as a data;

FIG. 6 shows a format of a file when programs are stored depending on their contents;

FIG. 7 shows a program structural informaiion of the subsystem;

FIG. 8 shows a format of a start message sent by a started subsystem;

FIG. 9 shows transmission and reception status of the message;

FIG. 10 shows a format of a start response message sent in response to the start message; and

FIG. 11 shows a process flow chart at the start of the subsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention is now explained with reference to the accompanying drawings.

FIG. 1 shows an overall configuration of a distributed processing system to which the present embodiment is applied. It comprises a loop transmission system 1 and a plurality of information processing units 11, 12, --- 15 connected thereto. As shown in FIG. 2, an i-th information processing unit li comprises a transmission system interface 40 which is an interface to a node control processor (NCP) 2 of the loop transmission system, a processor 50, a RAM 60 for storing programs and data of the processor, a ROM 70 which contains structural information of the information processing unit, and an interface 80 to I/O devices such as a disk and terminals. A disk device 20 and a terminal device 30 may be connected to the I/O interface 80 as shown in FIG. 1. The information processing units are interconnected through the transmission system 1 and there is no master-slave relation among the information processing units and they process asynchronously to each other.

FIG. 3 shows a format of a message which flows through the transmission system 1. In FIG. 3, numerals 101 and 107 denote flag areas which indicate the beginning and the end of the message, respectively, numeral 102 denotes an area in which a code (FC) indicating a content of a real data field (D) 105 of the message is set, numerals 103 and 104 denote areas for message controlling data SA and DN, and numeral 106 denotes an area for a frame check sequence (FCS). The transmission system reformats the data sent from the information processing unit 1i through the transmission system interface 40, into the message shown in FIG. 3 and sends it to the transmission line. The message sent to the transmission line circulates through the transmission line through the NCP's on the transmission line, and received by the transmitting NCP and erased thereby. On the other hand, each NCP detects the FC of the message received from the transmission line and compares it with an FC preregistered in the NCP by the information processing unit. If the received FC matches with the registered FC, the FC and the data D in the received message are sent to the processor 50. If the received message is not the self-sent message, it is sent to the next NCP.

In the present embodiment, the processor 15 of the information processing unit is used as a subsystem to which the program developing terminal 30 is connected, and the information processing unit 14 is used as a program editing subsystem which extracts a program from the data flowing through the transmission system, edits it and stores it in the disk. The program loading to the information processing unit 12 is explained below.

The operation of the information processing unit 15 to which the program developing terminal 30 is connected (hereinafter it is called a program developing subsystem) is explained. When a new program is developed in the program developing terminal, an input data FC (input FC), an output data FC (output FC) and a header indicating a program length are added to the program (which is relocatable), and they are sent to the loop transmission system through the I/O interface 80, processor 50 and transmission system interface. When the data is sent, the FC used in the message is a content code FC_(P) which indicates that the content is a program. Even if the input/output FC of the program hanges, the content code FC_(P) does not change.

FIG. 5 (a) shows a content (FC and a data field) of a message sent to the transmission system when the program developing subsystem develops a program P₁ having FC₁ as the input FC, FC₂ as the output FC and LP₁ as its length. In the present embodiment, the numbers of the input/output data of the programs are one, respectively. When the numbers of the input/output data are more than one, a plurality of input/output FC areas are prepared (FIG. 5 (b)). In sending the program, it is not necessary to know where the information processing unit to which the program is to be loaded is located in the system, but a new program, whenever it is developed, need only be sent to the transmission line. It is the subsystem having the program FC "FC_(P) " registered in the NCP that reads in the program sent by the transmission system.

The operation of the information processing unit 14 to which the disk device 20 is connected (hereinafter it is called a program editing subsystem) is now explained. In the NCP to which the program editing subsystem is connected, the FC_(P) which indicates the program has been registered as the FC. Each time the program flows through the transmission system, the program editing subsystem reads it in and stores it in the disk 20. FIG. 6 shows a format of storage. Since the input/output FC is written in the header of the program, the program is soored by using the FC as a key. In the present embodiment, the numbers of the input/output data of the program are one, respectively, but the program is stored by using input/output FC's where the number of input/output data are plural as input keys. In FIG. 4, the program shown in FIG. 5 (a) is sent from the program developing subsystem and it is read in by the program editing subsystem and stored in the disk. In FIG. 6, the program just read in is stored in the disk.

The operation of the information processing unit 12 to which the program is loaded is now explained. In the ROM 70 of the information processing unit 12, subsystem structural information (FIG. 8) indicating input/output FC's of the program to be loaded to the RAM 60 in the unit has been written. The information processing unit 12, when it is powered on, sends a subsystem start message to the loop transmission system in accordance with subsystem structural information (FIG. 7) stored in the ROM 70. FIG. 8 shows the subsystem start message. Since the subsystem structural information includes the input/output FC's for two programs, the number of programs (2) and the input/output FC's for the respective programs are added. The FC of the subsystem start information (FC start) is common to all information processing units which are started. The FC of the subsystem start information is registered in the NCP to which the program editing subsystem is connected. When the program editing subsystem receives the subsystem start information, it searches the disk by using the input/output FC attached to the data field as a key. If there is a program having a matching input/output FC, a subsystem start response message shown in FIG. 10 is prepared based on the matched program and its input/output FC, and it is sent to the loop transmission system. The format thereof is shown in FIG. 10.

After the information processing unit 12 has sent the start message, it operates in accordance with a flow shown in FIG. 11. After it has sent the start message, it sets a timer and waits for a predetermined time until it receives a start response message (steps 503, 504). If the time elapses, it increments a start failure counter, and if the number of times of failure reaches three, it sends a start failure message (step 507). If it receives the start response message, it checks whether all of the programs having the input/output FC's designated by the subsystem structural information have been received, and if there is an error, it retries the starting. If it has received all programs having the input/output FC's necessary in its subsystem, it sequentially loads the programs from the start response message (step 510). After the loading, all input/output FC's of the loaded programs are registered in the NCP. This is illustrated in FIG. 9.

In accordance with the present invention, a desired program can be loaded to a subsystem by the coordination of other subsystems without knowing the system configuration or the location of the program. Accordingly, the expandability and reliability of the program loading are improved.

The program developing subsystem sends the new program whenever and the other subsystems store the latest program. When other subsystem starts, the latest program is sent in accordance with the program structural information. Thus, whenever the subsystem starts, the latest program is loaded to the subsystem.

As to a revised version of the program, it is sent from the program developing subsystem to the transmission system and stored in other subsystem. Thereafter, the subsystem whose program should be revised is restarted. started. 

We claim:
 1. A method for loading a program in a distributed processing system including a plurality of information processing units interconnected by a transmission system, comprising the steps of:storing at least one program and its identifier in a memory of at least one of said information processing units; transmitting a message from an information processing unit, said message including a request for a program to be loaded into at least one of said information processing units; receiving said message and retrieving at least one stored program and its identifier based on said message from a memory of at least one information processing unit other than said information processing unit sending said message; transmitting said at least one stored program and its identifier retrieved from said memory; and selecting a program on the basis of said identifier from said at least one stored program being transmitted and loading the selected program in a memory of at least one information processing unit other than said information processing unit transmitting said stored program and identifier.
 2. A method for loading a program according to claim 1 further including the steps of:generating a program in at least one of said information processing units; transmitting said program and its identifier for storing in a memory of at least one information processing units; and receiving said program and its identifier, checking said identifier and storing said program, and its identifier in a memory of at least one information processing unit other than an information processing unit transmitting said program and its identifier for storing.
 3. A method for loading a program according to claim 1, wherein said selecting step includes the steps of:receiving said at last one stored program and its identifier; checking the identifier of said at least one stored program; and storing in a memory a selected program having an identifier corresponding to a specific identifier.
 4. A method for loading a program according to claim 1, wherein each information processing unit at initialization transmits a message which includes a request for a program to be loaded in said information processing unit transmitting said message.
 5. Apparatus for loading a program in a distributed processing comprising:a plurality of information processing units interconnected by a transmission system; wherein each information processing unit of said plurality of information processing units includes means for transmitting a program with a program identifier indicating the content of said program and means for receiving said program checking said program identifier, and storing in a memory a selected program having an identifier corresponding to a specific identifier; and wherein at least one of said information processing units includes means for retrieving a program from a memory based on a program identifier which is included in a request for program loading command transmitted as part of a message from an information processing unit, and means for transmitting said retrieved program with its program identifier.
 6. Apparatus for loading a program according to claim 5 wherein each information processing unit further comprises means for transmitting a message which includes a request for program loading command.
 7. An apparatus for loading a program according to claim 6 wherein each information processing unit further comprises means for transmitting a message which includes a request for program loading at initialization of said information processing unit. 